The present invention relates to an abrasive and a method of abrading a work piece, more precisely relates to an abrasive machine, which has an upper abrasive plate and a lower abrasive plate for abrading both faces of a work piece, and a method of abrading a work piece with said machine.
In a conventional abrasive machine having an upper and a lower abrasive plates, a work piece is sandwiched between the abrasive plates, and the abrasive plates are rotated in the opposite directions with feeding slurry to the work piece, so that both faces of the work piece can be abraded. The conventional abrasive machine (see Japanese Patent Gazette No. 11-262862) is shown in FIG. 5. The abrasive machine includes: an upper abrasive plate 10 and a lower abrasive plate 12, which are rotated in the opposite directions; a sun gear 14: an internal gear 16; and carriers 18. The carriers 18 are provided between the abrasive plates 10 and 12, and a gear (not shown), which engages with the sun gear 14 and the internal gear 16, is formed along an outer edge of each carrier 18. With this structure, the carriers 18 are capable of spinning about their own axes and orbiting along the internal gear 16. By rotating the abrasive plates 10 and 12, upper faces and lower faces of work pieces 20, which are respectively held in through-hole of the carriers 18, can be abraded by the abrasive plates 10 and 12.
The lower abrasive plate 12 is held by a lower holder 22, and the lower holder 22 is rotatably supported by a base 24. The lower holder 22 is rotated by a rotary shaft 22a, so that the lower abrasive plate 12 is rotated. The upper abrasive plate 10 is rotated by a drive shaft 26 and engaging members 28 and 29.
The sun gear 14 is rotated by a rotary shaft 30. A casing 32 supports the internal gear 16.
In the abrasive machine shown in FIG. 5, a plate 40 is provided above the upper abrasive plate 10, a slurry ring 42, whose sectional shape is a U-shape, is provided to the plate 40, and connecting pipes 44 and connecting tubes 46 are connected to the slurry ring 42, so that the slurry ring 42 is communicated with slurry holes 48 formed in the upper abrasive plate 10. Valves 50 for controlling amount of flow are respectively provided to the connecting tubes 46. The plate 40 is rotated in one direction together with the upper abrasive plate 10, and slurry supplied to the slurry ring 42 is fed to the work pieces 20 via the connecting pipes 44, the connecting tubes 46 and the slurry holes 48. The valves 50 adjust amount of the slurry fed to the slurry holes 48. For example, much slurry is fed to the slurry holes 48 near the center of the upper abrasive plate 10.
In the conventional abrasive machine, the slurry is uniformly fed to the work pieces 20 by adjusting the amount of the slurry supplied to the slurry holes 48 of the upper abrasive plate 10. However, as shown in FIG. 5, the slurry flows downward from the slurry ring 42 by gravity or own weight. Therefore, it is difficult to control the amount of the slurry because the slurry holes 48 must be properly selected and the flow of the slurry must be precisely controlled.
In the abrasive machine, the upper abrasive plate 10 is lifted or moved upward until reaching an uppermost position when the work pieces 20 are exchanged, maintenance is taken place, etc. At that time, some work pieces 20 stuck on an abrasive face of the upper abrasive plate 10 are lifted together with the upper abrasive plate 10. If the work pieces 20 are lifted together with the upper abrasive plate 10, the work piece 20 fall therefrom, and they are damaged. These days, the work pieces 20 are large and thin, so they are apt to be stuck on the upper abrasive plate 10. Especially, in the abrasive machine capable of automatically feeding and removing work pieces, sticking the work pieces onto the upper abrasive plate must be prevented.
To solve the problem of sticking work pieces onto an upper abrasive plate, some methods have been proposed. For example, mist of a fluid is jetted from the upper abrasive plate to work pieces (see Japanese Patent Gazette No. 11-226864); jet holes are formed in the upper abrasive plate, and high pressure air is jetted from the jet holes toward work pieces so as to peel off the work pieces (see Japanese Patent Gazette No. 9-66448); an ejecting member, which is usually located away from the upper abrasive plate, is actuated to mechanically eject work pieces from the upper abrasive plate (see Japanese Patent Gazette No. 6-55436); a compressed fluid, e.g., compressed air, is jetted from the upper abrasive plate so as to peel off work pieces (see Japanese Patent Gazette No. 58-171825).
However, even if jet holes for jetting a compressed fluid are formed in the upper abrasive plate so as to peel off work pieces, the jet holes are independent of the slurry holes. Thus, if arrangement of the slurry holes has priority over that of the jet holes, the arrangement of the jet holes are restricted so that the jet holes cannot be located at ideal positions. Further, in the abrasive machines capable of abrading various types of work pieces, jet holes cannot be always located at ideal positions because the positions of the jet holes are fixed.